Logic Expressions: What does bar over letters mean?

[Neil543]

Hello to all,

If I have an expression that I am being asked to simplify the expression considering that A=0, what am I being asked to do? What do I need to understand? I really don't have the foggiest idea.

I understand that the line above the first letter B indicates that it is not B but what does the line above the line mean in the centre of the expression?



I am genuinely grateful for all the help offered.

Thanks
Neil

 

[Steven G]

The line above any expression means NOT that expression. Since I do not know how to write a line I will use ' instead. So (AxB' +C)' means NOT (AxB' +C)
Also what are A, B C and D? Are they sets? I would think not since you said A=0.
You can use any letters you like, but you need to define them!

 

[pka]

If I have an expression that I am being asked to simplify the expression considering that A=0, what am I being asked to do? I understand that the line above the first letter B indicates that it is not B but what does the line above the line mean in the centre of the expression?

View attachment 14102

The title of your post is logic expressions however none of the above symbols are used in standard logic courses, well maybe Boolean logic. So you must tell us what is going on there.

 

[Neil543]

The title of your post is logic expressions however none of the above symbols are used in standard logic courses, well maybe Boolean logic. So you must tell us what is going on there.

Yes, sorry about that. It's Boolean logic.

I am being asked to simplify the expression and to consider that A=0. From the digging that I have done isn't A=0 a given?

 

[Dr.Peterson]

If I have an expression that I am being asked to simplify the expression considering that A=0, what am I being asked to do? What do I need to understand? I really don't have the foggiest idea.

I understand that the line above the first letter B indicates that it is not B but what does the line above the line mean in the centre of the expression?

View attachment 14102

Yes, sorry about that. It's Boolean logic.

I am being asked to simplify the expression and to consider that A=0. From the digging that I have done isn't A=0 a given?

It will be very helpful to us if you tell us something about the context of your question. Why are you trying to answer this without knowing what the symbols mean? What do you know about Boolean logic, on which we can base an answer?

A=0 is a given, in the sense that they have given you that fact for this problem. It is not a given in the sense of something you are expected to know -- it is not true in general. Presumably you know that 0 means "false" and 1 means "true".

In this context, "+" means "or", and "x" (more commonly, a dot) means "and". In order to carry out this simplification, you will need to know various rules, such as that 0 + x = x (that is, false or anything has no effect), so that A + B' = B'. Have you learned these things?